1. Field of the Invention
The present invention relates to a slide device for vehicle or automotive seat, which allows a vehicle or automotive seat to be slidingly movable via a slide rail structure in the fore-and-aft direction. In particular, the invention is directed to a powered long slide device for vehicle or automotive seat, wherein an upper slide element on which the seat is mounted is slidingly moved by a motor and control system on and along a long lower track element fixed on the floor of vehicle or automobile.
2. Description of Prior Art
In general, a long slide device is used, for instance, in a van-type automobile, such as a mini-van car or the like, the long slide device normally comprising a pair of lower track elements or lower rails of a relatively large length, i.e. a long lower ail, suited for mounting on an enlarged rear cabin space in the mini-van car, and a pair of upper slide elements or upper rails slidably fitted in the long lower rail. An automotive seat is fixedly mounted on the pair of upper rails, and therefore, the seat can be slidingly moved on and along the pair of long lower rails forwardly and backwardly in the wide rear space in the van-type automobile.
But, it is a troublesome labor for a user to manually move the seat along such long lower rails. For that reason, there has been made available a powered long slide rail device which employs motors and electrical control systems to cause forward and backward sliding movement of the upper rails on and along the lower rails.
For example, such powered long slide rail device has been disclosed from the Japanese Laid-Open Patent Publication No. 11-11186, according to which, a long lead screw element is fixed to and along a long lower rail, whereas a rotary nut element, very short relative to such long lead screw element, is provided in an upper rail so as to be in a partial threaded engagement with the long lead screw element, the rotary nut element being rotated by a motor under an electrical control, so that operation of the motor causes rotation of the rotary nut element about the lead screw element. Naturally, the rotary nut element is moved in either of forward and backward directions on and along the lead screw element, thereby causing relative forward and backward movement of the upper rail (or seat) on and along the long rail.
Incidentally, by and large, the body of automobile, in which the slide rail device is installed, is formed by putting together a plurality of panels and plate members as by spot welding. Due to such spot welding, distortion and twisting may frequently occur among those panels and plate members, resulting in a structural deformation or error in shape of the automobile body as well as in the floor of the automobile.
When it comes to mounting the foregoing long lower rail disclosed in the Patent Pub. No. 11-11186 upon the floor of automobile, the foregoing structural deformation or error in shape of automobile body will cause undesired deformation in the long lower rail because the fragility of the long lower rail becomes greater with its increased length and also cause undesired torsion or twisting in the lead screw element. Hence, it is highly possible that the threaded engagement between the rotary nut element and the lead screw element will become poor, which will make it difficult to keep a smooth relative movement of the rotary nut element along the lead screw element. Further, in the case where a seat belt is connected with the upper rail in which the rotary nut element is provided, it is of a great likelihood that a great upward load applied from the seat belt to the upper rail in such an emergency case as a collision will forcibly draw the rotary nut element upwardly from the long lead screw element, as a result of which, the long lead screw element will be bent or deformed, and therefore, it will be even much difficult to repair the slide rail device for re-use purpose.
The same goes for the case where rack and pinion gears are employed in the long slide rail device, because the rack gear has to be long for mount in and along the long lower rail and will become vulnerable to a local great load applied from the pinion gear which is connected with the upper rail, thus encountering the same problems as stated above about the combination of lead screw and rotary nut elements.
In view of the above-described problems, it is possible to use a tape-type transmission mechanism in a powered slide rail device, for example, which uses elastic tapes as a transmission means for causing relative movement between upper and lower rails, as disclosed from the Japanese Laid-Open Patent Publication No. 9-277856. According thereto, tapes are movably connected between the upper rail and a motor drive mechanism including a drive pulley with which the tapes are partially engaged, so that operation of the motor drive mechanism causes rotation of the drive pulley to move the upper rails forwardly on and along the lower rail. However, application of this prior art mechanism to the long slide rail device will raise the following problems: (i) As stated above, the mechanism disclosed is for moving the upper rails only in the forward direction along the lower rail, not moved backwardly. To enable forward and backward movement of the upper rails, the construction and operation systems of the associated drive mechanism will become quite complicated, and (ii) Since the tape used is long and partially engaged with the drive pulley, a free end portion of the tape extends outwardly from the drive pulley to a greater length than required, which is indeed true of the long slide rail. That is, because of the long lower rail, long tapes are used to cause translation of the upper rail in a long distance along that long lower rail, as a result of which, it is troublesome and difficult to store the free end portions of the long tapes, and in that case, a whole structure of slide rail device will be rather complicated, with an increased number of parts and a high cost involved. Further, the Pub. No. 9-277856 shows a locking device having a plurality of lock holes and a lock plate being engageable into a selected one of the lock holes, but no description is given about such locking device. In other word, this prior art is entirely silent for an interlocking relation between the locking device and the foregoing tape-type transmission mechanism, and therefore, it is impossible with that prior art system to insure locking engagement of the lock plate into a selected one of plural lock holes in a good-timed interlocking relation with the forward and backward sliding movement of the upper rail along the lower rail.